Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
X = [input() for _ in range(H)]

dist = [[0] * W for _ in range(H)]
dist[0][0] = 1
q = deque([(0, 0)])

while q:
    u, v = q.popleft()
    for i, j in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
        if (not (0 <= u + i < H and 0 <= v + j < W)
                or X[u + i][v + j] == "#"
                or dist[u + i][v + j] > 0):
            continue
            
        dist[u + i][v + j] = dist[u][v] + 1
        q.append((u + i, v + j))

if dist[-1][-1] > 0:
    print(W * H - dist[-1][-1] - sum(s.count("#") for s in X))
else:
    print(-1)